1. Technical Field
The present invention relates to an organic electroluminescence device such as an organic electroluminescence display unit manufactured using, for example, an inkjet method and an optical device such as a color filter.
2. Related Art
In an organic electroluminescent device manufactured using an inkjet method, a low-molecular luminescent material or a polymer luminescent material is used to form an organic electroluminescent layer as a light-emitting layer. The luminescent layer formed of the low-molecular luminescent material is typically formed using a dry method such as a vacuum deposition method. For this reason, it is thought that it is difficult to form the luminescent layer made of a low-molecular material on a large panel in a uniform thickness. The luminescent layer made of a polymer material is typically formed by coating a coating solution obtained by diffusing and dissolving the polymer luminescent material in a solvent on a panel using a coating method such as a spin coat technique. Therefore, it has been thought that it is difficult to manufacture a full color display panel by coating a coating solution containing luminescent materials for each color.
In this situation, JP-A-10-153967 discloses an organic electroluminescent device capable of implementing a full-color display by coating organic electroluminescent materials having red and green colors using an inkjet method and depositing a luminescent material having a blue color on a predetermined area and the organic layers emitting red and green colors. This document also suggests that this organic electroluminescent display device can be applied to an organic electroluminescent display device manufactured on a large panel.
In addition, when the luminescent layer is formed using an inkjet method, a flat luminescent layer can be provided by coating a liquid droplet containing an organic electroluminescent material on the areas defined by a partition for partitioning the luminescent layers and then drying out the liquid droplet. In this case, the behavior of liquid droplet when the solvent is vaporized from the liquid droplet depends on the solvent and the organic electroluminescent material contained in the liquid droplet, and a drying condition, Therefore, in order to provide uniform brightness from the luminescent layer in each pixel and an entire panel, a manufacturing should be carefully processed so as not to damage the flatness of the luminescent layer obtained by drying out the liquid droplet. In consideration of this point, JP-A-2002-252083 proposes to coat the liquid droplet even on areas originally not functioning as a pixel area in order to prevent the liquid droplet from being dried out too fast.
In addition, JP-A-2002-148429 discloses a technique for improving wetness of the liquid droplet on the surfaces of the partitions to flatten the luminescent layer formed after the dry-out process by performing a surface roughening for the surfaces of the partitions that define the areas where the liquid droplet containing the organic electroluminescent material is coated, i.e., the area where the luminescent layer is to be formed.
In this kind of organic electroluminescent device, the luminescent portion formed by coating the organic electroluminescent material to further improve a numerical aperture is preferably not circular but noncircular in a plan view. More specifically, in order to further Improve the numerical aperture of the entire organic electroluminescent device, an arrangement where the luminescent portions having an anisotropic cylindrical form extending along a certain direction in a plan view are arranged in an array form is more efficient than an arrangement where the luminescent portions having a circular shape in a plan view are arranged in an array form.
However, when a liquid droplet is coated on the cylindrical form area surrounded by the partitions to provide the luminescent portions having an isotropic shape in a plan view, a force applied from the side wall surface of the partition to the coated liquid droplet is anisotropic, and a force applied from each side surface wall adjoining the liquid droplet to the liquid droplet when the liquid droplet is dried is irregular for each direction. Therefore, it is technically difficult to provide a flat luminescent layer.
In consideration with the aforementioned technical problems, it is difficult to provide a luminescent layer having a sufficiently uniform thickness based on the JP-A-10-153967and the JP-A-2002-252083. Even when the technique disclosed in JP-A-2002-148429 is used, it is difficult to flatten the surface of the liquid droplet by adjusting the force applied from the side wall surface that defines the anisotropic area on which the liquid droplet is coated to the liquid droplet in each direction just through a surface roughening on the side wall surface of the partition, and it is also difficult to provide a flat luminescent layer through the dry-out process. When the luminescent layer is formed on each of a plurality of pixels defined by the partitions on a large panel using an inkjet method, it is difficult to provide a flat luminescent layer by drying out the coated liquid droplet coated in each area due to inconsistent drying rate generated depending on locations between a portion near edges of the panel and a portion near the center of the panel.